Valve mechanism



Aug. 27, .1946.

' VALVE MECHANISM Filed sept, 14, 1944 INVENTOR.

` Y P.. J. Bumm-T1 I 2,406,662

Patented Aug. 27, 1946 yUNITED gsTATlazs PATENT Aofi-Fica 2,406,662 VALVE MECHANISM Paul J. Burchett, Glendale, Calif.

Application September 14, 1944, Serial'No..553,978

` 14 Claims. 1

This invention relates to valve Vmechanisms and more particularly to valve Vmechanism for controlling .the flow of fluids in a conduit.

The valve mechanism of the present invention is particularly adapted for Iuse as a check valve in theV oil lines of anaircraft engine although its use. is .not limited to that field. rI'he mechanism lcan be used in any fluid installation Where a simple but very effective control is desired.

In present day aircraft engines check or nonreturn valves are provided at the jointure between the oil supply lines and those leading to the engine. sisted of ball or cone valves normally held open by some suitable means against the action of springs. When the oil supply'lines are removed from the lines of the engine the means holding the balls or cones away from their seats are rendered inoperativev and lthe springs urge the balls or cones against the seats and seal the open ends of the lines against leakage.

The balls or cones of these valves must of necessity be larger in diameter than the lines With which they are used. Thus the Valve housing must be of a diameter considerably larger than theY diameter of the line to permit the oil to flow around the ball or cone when the same is displaced from the seat. This complicates assembly of the lines and the engine in the fuselage of the aircraft. These valve mechanisms are also subject to the criticism that they restrict the ow of the oil through the lines as the oil must flow around the ball or cone to pass the valve formed' by the same.

The valve mechanism of .the present invention obviates those difficulties for the same is no larger in diameter than the line with Which it is to be used. Thus the valve herein disclosed may be assembled with an oil line and passed with the line through an opening in a structural part. This feature of the invention eliminates the necessity of assembling theV valve after the line has been passed .through the opening as is required in the assembly of the previously proposed ball or cone valves.

The'valve mechanism in one form of the invention comprises a pair of identical trough-shaped clappers mounted so that when the edge faces thereof are in facewise engagement the same substantially form a iiattened conically shaped assembly. vThe edges faces of the clappers are each formed with a fulcrum'point about which each clapper rocks relative to the other. A resilient member encircling the lbase of the conically shaped assembly is displaced from therful- These valves have generally con-y crum point and the force exerted by the resilient member is .sufficient to normally hold the clappers closed with the entire surfaces of the edge faces thereof in faceWise engagement. When the clappers arein this relative position the Valve formed by the same is closed and when the clappers Aare rocked about V.the respective fulcrum points to move the edge faces in opposite directionsathe valve is open.

The clap-pers need be' only of. such a size as to permit their insertion with the line when assembled' and held rtogether by the encircling resilient member. Thus no enlarged housings are required in the valve mechanism of Ythe present invention te complicate assembly of the oil lines and engines with the fuselage of the aircraft. u The clappers when open, as the interiorV surfaces form a substantially cylindrical passage, offer relatively little obstruction to the ow of oil thru the valve formed by the same. 'Ihus the yinherent obstructional disadvantage of the ball or cone valves previously proposed is overcome in the valve mechanism lof the present invention.

The meeting faces of the clapper are substantially elliptical in shape and present relatively large areas for effectively sealing the passage between theclappers when 'the same are closed. If desired the seal can be augmented by forming one face with some suitable means and the other face with cooperating means forl increasing the seal when the clappers are in closed position.

The valve mechanism `of the present invention can also be effectively used as a check valve in a line where the flow through the same can be used to operate the clappers or leaves. In this form of the present invention, the clappers are held open by the normal flow of the fluid and closed by either a cessation of flow or a reversal in the di rectiony ofV fiow.

Other features and advantages of the present invention Will be apparent from the following description taken in connection with the accompanying .drawing in which: y

Figure 1i is a View partly in section and partly in elevation of one embodiment of the valve mechanism of the present invention;`

Figure 2 ssection taken along line 2-2 of' Figure 1;

Figure 3 is an elevational View showing in open position a modified form of the valve of the present invention, the broken line illustration showing the valve in closed position;

YFigure 4 is a View partly in section and partly in elevation ofthe valve shown in Figure 1;

Figure 5 is a section taken along line 5--5 of Figure 3;

Figure A6 is a sectional view of another form of the valve mechanism of the present invention; and

Figure 7 is an exploded View of the mechanism of Figure 6 The valve mechanism of the present invention may take the form illustrated in Figure 1 in which I indicates a line or conduit leading to the engine of an aircraft. The line is passed through an opening in the firewall I I, the opening being sealed by some suitable means such as the grommet I2.

The line IIJ is to be connected to a linek I3 leading from the cil storage means As it is many times necessary to detach the engine line ID from the storage line I3 it has been necessary to mount at the jointure between the two lines some valve mechanism for preventing oil from draining' from both the engine and storage means when the lines are disconnected.

' The Vvalve mechanism shown by Figure 1 is well adapted to serve as a check valve for each line. In this adaptation of the present invention, a valve is disposed in each line and is so arranged therein that oil can not flow or drain from either line after the lines have been separated or disconnected. Each valve unit comprises a pair of substantially trough-shaped or scoop-like clappers or leaves I4. Each clapper is formed with an open end and the concavity decreases from the open end toward the opposite end of the same. f

The clappers are mounted with their concave surfacesin juxtaposition as illustrated in Figure 2. Thus the edge faces I of the clappers face each other and facewisely engage each other when the clappers are closed. As the outline of the edge face I5 of each clapper is substantially that of half an ellipse the two clappers when closed form a conoidal member such as clearly illustrated in full lines in Figure 4 and in broken lines in Figure 3.

The'edgeV face adjacent the rear or larger end of each clapper is cut back as shown at I6 to the end that the Vclappers may be rocked about the fulcrums formed at I'I. It will be seen that when the clappers are rocked toward each other they form a bivalvular closure means and effect a clam-like joint but when they are rocked in the opposite direction to separate the smaller ends of the same a substantially cylindrical shaped passage is formed therebetween.

To prevent the clappers from separating and to-maintain the edge faces in engagement, a ring I8 of some resilient material such as rubber encirclesv the clappers and yieldably urges the same together. The fulcrums I1 of each clapper are displaced rearwardly of the ring I8, which is held in a suitably formed groove extending about the clappers, so that the ring acts through the lever arm formed by the displacement of the ring relative to the fulcrum I1 to normally hold the edge faces I5 of the clappers in engagement.

The pair of clappers are mounted within a tubular member or mounting band I9 having a reduced or restrictedportion formed by internally flaring the band I9 intermediate the ends thereof to forman annular shoulder 20. The inner diame ter of the shoulder 2,@ is lessthan the outer diameter of the ring I8 so that the ring and clappers are held against movement in one direction longitudinally of the band I9 by the engagement between the ring I8 and the shoulder 20.

To hold the clappers against turning relative to the mounting band I9 as well as to prevent their moving longitudinally of the same, the opposite ends of a pair of. C-rings 2I are passed through openings in the band I9 and engaged in arcuate slots 22 formed in the tail portions of the clappers I4.

In the form of the invention illustrated in Figure l, the mounting band I9 is substantially the same diameter as the lines I0 and I3. Thus, as shown in the figure referred to, a band with its associated elements when mounted at the free of the aircraft. y

end of a line forms a continuation thereof.

As the valves formed by the clappers III will normally be closed due to the action of the encircling ring I8, means are provided, in the embodiment of the invention illustrated in Figure l, for holding the clappers apart as long as a flow of oil is desired from line .I 3 to line I0.

Although any means desired may be used to hold the valve formed by the clappers open, it is now preferred to use a member 23 having a pair of eppcsitely extending tongues 24. The member 25 is fixedA within a tubular casing 25 by spot welding a' pair of flanges 2li to diametrically opposed portionsof the casing as best shown in Figure 2. The casing has a diameter equal to the diameter of the mounting bands I9 and a length less than the member 23. Thus the tongues 2li project outwardly ofthe casing 25 at opposite ends thereof. The casing 25 is mounted between the' bands I9 and the opposite ends thereof are held in engagement with the adjacent ends of the bands I9 by a pair of connectors 21 and 28, each comprising a rubber packing sleeve 29 and a plurality of clamping rings 3|,

The tongues as they extend beyond the casing 25 project between the clappers I4 and normally tend to hold the same apart so that oil may flow from the line I3 into the engine line Ill. It can be seen from Figure 2 that the clappers I4, as the same when open form a substantially cylindrical passage, offer little obstruction to the flow of oil. The member 23, although it extends across the iow through the casing, forms only a slight obstruction to the same because of the extremely small cross sectional area presented by the end faces of the tongues. p

.Whenit is desired to disconnect the lines I0 and i3, the clamping ring adjacent the inner end of the connector 2l is loosened until the line I3 and itsas'sociated valve can be moved to the left as viewed in Figure 1. .As the casing 25 is still held tightly by the connector 28, the clappers of the valve associated with the line I3 will move out of engagement with the tongue 24 holding them apart and thering I8 will move the clappers together to bring the edge faces thereof into engagement and thus close the line I3.

The mounting band I9 associated with the line I3 will -move relative to the casing 25 until a pin 32 carried bythe band engages the end of a groove 33 formed in the tongue 24. After the pin has moved the length of the slot the casing 2 5 will move with the band as the line I3 is pulled away from the line III and withdraw the other tonguefrom its position intermediate the clappers forming the valve of the line I. As soon as this tongue has been withdrawn from between the clappers the same will be closed by the ring I8 and oil' will` .be prevented from draining out of the engine. I 1 y .In use, the disconnecting movement should be rapid to insure that the tongues are quickly withdrawn from their normal position between theA clappers; valves formed by `theclappers vor leaves will close and useal the lines just as rapidly as the tongues are mcved'out of theirnormal position.

As' the pressure against the Vclappers urge thev resilient rings |,8 back into engagement with they internalr shoulders 20v and tightly hold the rings in-engagement `with `the same, no oil canlea'kthe edge faces are in i'lrm contact is remarkably good. f

IWith both lines now sealed `'against the loss of oil, the twolines can be disconnected. It'Will beseen that the member 23 will, because of the pin and slot connection, remain with the valve associated with the line t3. As the valves formed no enlarged protuberance at the ends of the lines,` the latter can be easily withdrawn through any apertureor passage large 'enough to pass the lines if it should benecessary to disassemble the linesv from such structural 'parts of the aircraft as'theflrewall I|-.

`If desired, means may Vbe provided on the edge faces of the clappers of the vvalve mechanism of the present invention for increasing the seal eifected bythe engagement of the faces. Thus as'shown in Figure 5, the edge face of the clapper 35 can be formed with a lip 35 and the edge face of the other clapper with a continuous groove 3'! for receiving the lip 35 when the clappers are closed. It will be understood howeverthat the means may take other forms for obviously a sealing'gasket orstrip Vmight be fixed to the edge face of one clapper or even both clappers if desired.

There is shown in kFigure 6 and 7 another valve mechanism embodying the features of the Vpresent invention. This mechanism comprises a tubular casing 38 formed with an internal shoulder carrying a suitable gasket 39. A ring 4| formed with an inturned knife edgek or shoulder is concentrically mounted' within the casing 38 and adapted to be held againstthe gasket 39 by a sleeve 42 and a shouldered coupling member 43 threaded into lthe casing 38. A second gasket 44 is mounted over the threaded portion of the coupling member 43 to seal the connection between the casing and the latter.

In this Aembodiment of the present invention, the edge faces 45 of the two clappers or leaves 46,'like the edgeY faces of the clappers I4 of the earlier described form of the present invention, areeach formed with a high point so that the clappers 46, when the edge faces thereof are in engagement, can rock about the fulcrums formed by the high points. The outer surface of each clapper 46 is provided with afrecess so formed that when the clappers are brought together with their edge faces in engagement a relatively wide, continuous groove 41 is formed in the outer surfaces of the assembled clappers. The groove 41 thus formed receives a resilient O-ring 48 It werbe understos *that the which holds the edge faces of the clappers in entheclapp'ers in the desired relative position butV yetfpermits the rocking movement described above. Y

To permit the'valve mechanism of Figure i6'-v to-be connected into a fluid line theV casing 38 and the coupling .member 43 are each \formedi with threaded portions 49 and 5i respectively,Y the orientation Aof the valve mechanismk depending on the direction vof normal ow vinthe line.

It will be seen that when the clappers/Mendthe encircling rings 4l and 43 Aare mounted in the casing 38 and the sleeve 42 and the coupling member 43 assembled therewith, the valve mechanism so formed will permit a flow onlyin the direction of the arrow of Figure 6 when theI pressure is sufficient ytoA overcome the action of the Oring 48.

It should now be understood'that the clappers or leaves 46 will remain open as long as the flow in the direction of the arroW'EZ of Figure V6 i-s together and close' the valve formed by the same.

If the flow should be reversed in direction the clappers will also close and the 'pressure against the same Will more'rrnly Vvhold the edge faces of the clappers in engagement. Thus it' will be seen that .the seal will bev even kmore effective when a reverse flow does occur.

As the formof the valve mechanism shown in Figures 6 and 7 is intended to be' used in a high pressure system means must be provided for re lieving the O-ring of the' forcev exerted bythe pressure against the clappers when the same are closed by a reversal in the flow. In the form of the invention now preferred, Lthe force Yexerted against the clappers is taken in most part by an annular shoulder `53 formed internally of the casing 38 and against which the clappers seat when closed. To permit the clappers to properly closethe seat should be s formed that the same is substantially normal to the clappers when thel same are closed.

'The width of the groove receiving the rings 4l and 48 is such that the clappers may move' slightly in a direction aXially'of the casing Saso that the pressure exerted on the clappers *when` the flow is opposite to normal will causelthe O-ring to move back and be firmly held `against the shoulder of the ring 4l.' This Veffectively seals the joint `between the rings and prevents anyv leakage around the valve mechanism without placing too great a pressure on the O-ring 48.

It will be seen that in all forms of the invention illustrated the sealing action of the biva-lvular closure is enhanced by the pressure exerted against the clappers upon a flow in the direction opposite to the desired or normal direction ofow. All embodiments of the invention rherein shown and described also are capable'of securing a fluid tight seal without unduly restricting the normal flow When the valves are open.

Although the now preferred embodiments Vof the present invention have been illustrated and described herein, it should be understood thatr the invention is not to be limited thereto for it issusceptible to changes in form and detail within the scope of the appended claims.

I claim:

1. A valve mechanism comprising a pair of substantally trough-shaped clappers having one end open andV decreasing in depth toward 'the other. The'4 groove also 7 other end; yieldable means circumscribing said clappers and normally holding the edgerfaces thereof in facewise engagement; means on said edge faces forming fulcrums whereby said clap-j pers may rock relative to each other; a casing for housing said clappers; means for holding said clappers within said casing; and an annular shoulder formed internally of said casing, said circumscribing means adapted to engage said shoulder and seal the annular passage formed between said clappers and the inner wall of said casing. i

2. A valve mechanism comprising a casing; a pair of concave clappers mounted within said casing with the concave surfaces thereof in juxtaposition, each clapper having an open end and decreasing in depth from said openend to the opposite end thereof; yieldable means encircling said clappers and normally holding the edge faces thereof in facewise engagement; the edge face of each clapperbeing cut away adjacent the open end thereof to form fulcrums about which each clapper may rock relative to the other, said clappers forming a bivalvular means closing said casing when in said normal position, said clappers being relatively movable about said fulcrums to a position in which said shallow ends are spaced apart; and an inturned shoulder formed within said casing and adapted to be engaged by said encircling means to seal the annular passage between said clappers and said casing.

3. A valve mechanism of the type described comprising, a tubular casing; means for connecting said casing into a fluid line; conoidal bivalvular means movably mounted within said casing for movement longitudinally of the same, said means comprising a pair of scoop-like clappers mounted with their concave surfaces in juxtaposition, each clapper being rockable on the edge face of the other clapper from a closed position to an open position; resilient means encircling said clappers and normally holding the same with the edge faces in facewise engagement; and means within said casing for taking the longitudinal thrust of the clappers when the fluid is exerting a force on the same in closed position.

4. A valve mechanism comprising a pair of scoop-like clappers; each clapper open at the large end thereof and having an edge face formed with a pair of fulcrums adjacent the larger end thereof; means encircling said clappers for resiliently holding said clappers with the edge faces thereof in facewise engagement, said means'permitting each clapper to be forced about the fulcrums of the other clapper; a casing housing said clappers; means for connecting said casing into a fluid line, said clappers closing said casing to a flow of fluid when said edge faces are in facewise engagement, said casing being open to the flow when said clappers are forced apart about said fulcrums; and means cooperative with said encircling means to seal the annular passage between said clappers and said casing when said clappers are closed and the flow is exerting a force against said closed clappers.

5. A Valve mechanism comprising a pair of scoop-like clappers; each clapperopen at the large end thereof and having an edge face formed with a pair of fulcrums adjacent the larger end thereof; resilient means encircling said clappers, said means being displaced from said fulcrums and normally urging each clapper about said fulcrums toward the other clapper whereby-said clappers are normallyheld with the edge faces thereof Yin facewise engagement, said resilient means permitting said clappers to be rocked relatively to each other about said fulcrums whereby said clappers can be movedgapart to form a substantially cylindrical passage therebetween; a casing for housing said clappers for movement longitudinally of said casing; means for limiting said longitudinal movement of said clappers between alternate positions in said housing; means for connecting said casing into a fluid line, said clappers in the normal position thereof closing said casing to a flow of fluid, said casing being open when said clappers are rocked apart to form said cylindrical passage.

6. A valve mechanism comprising a pair of scoop-like clappers mounted on their edge faces for rocking movement relative to each other about fulcrums formed adjacent the larger ends of said clappers, the edge faces of said clappers intermediate said fulcrums and the smaller ends thereof being uniplanar and adapted to form a seal when in facewise engagement; resilient means encircling said clappers intermediate said fulcrums and the smaller ends of saidv clappers Vfor normally holding said edge faces in engagement, said resilient means permitting said clappers to be rocked about said fulcrums to move said edge faces out of engagement and the smaller ends of said clappers apart to form a substantially cylindrical passage between said clappers; a tubular member having an annular shoulder formed therein; means for mounting said clappers within said member with the encircling means engaging said shoulder and cooperating with the samelto seal the passage between said clappers and said tubular member;

and means for connecting said tubular member into a fluid line.

7. A valve mechanism comprising a pair of scoop-like clappers mounted on their edge faces for rocking movement relative to each other about fulcrums formed adjacent the larger ends of said clappers; a lip formed on the face of one of said clappers intermediate its fulcrum and the smaller end thereof, the face of the other of said clappers being formed with a groove for re ceiving said lip and forming a seal when'said clappers are in facewise engagement; a ring of resilient material encircling said clappers intermediate said fulcrums and the smaller ends of said clappers for normally holding said edge faces in engagement, said ring permitting said clappers to be rocked aboutrsaid fulcrums to move said edge faces out of engagement and the smaller ends of said clappers apart to form a passage between said clappers; a tubular member having an annular shoulder formed therein; means for mounting said clappers within said member with the ring encircling said clappers engaging said shoulder and cooperating with the same to seal the passage between said clappers and said tubular member; and means for connecting said tubular member into .a fluid line.

8. A valve mechanism comprising a pair of scoop-like clappers mounted on their edge faces for rocking vmovement relative to each other about fulcrums formed adjacent the larger ends of said clappers; means carried by the edge faces of said clappers intermediate said fulcrums and the smaller ends thereof for forming a seal when said faces are in facewise engagement; resilient means encircling said clappers intermediate said fulcrums and the smaller ends of said clappers for normally holding said edge faces in engagement, said resilient means permitting said clapc 9T; pers;` toi; berocked: abouttsaid; fulcrunrsY to: move saidledgei-faces1-out'; ofxengagement to; formifa passage hetweensaid:l clappers; a-.tubular member havingiizan. annular-;shoulder .i formed therein; means'f for'. mounting` saidrclappers; within said member. with. the kencircling:.meansk engagingsaid shoulder and cooperating with; the-'same to; seal the passagezbetweensaid clappers andsaid tubular member; and means for connectingA said tubular member into a fluid line.

9. Avalve mechanism for sealing the ends of a pair of fluid lines when the same are disconv nected comprising a tubular member adapted to be mounted to the open end of each line; a pair of scoop-like clappers mounted within each member, said clappers being Vmounted on their edge faces for rocking movement relative to each other about fulcrums formed adjacent the larger ends of said clappers; resilient means encirclingV said clappers and normally holding the edge faces thereof in facewise engagement, said resilient means permitting said clappers to be rocked about said fulcrums to form a cylindrical passage therebetween and concentric with said tubular inember; and means for interconnecting said lines, said means including means for engaging the clappers of each tubular member and forcibly rocking the clappers of each tubular member 1.0,' between concentric.: with! saidtub-ularfmember; a tubular; memberadapted to'be inserted between saidmounting: bands, to formk a continuation. of saidv lines; meansl carried by said tubular member and extending outwardly ofthev opposite ends thereof for receptionbetween eachpair,l ofv clappers for holding thesmallenendsvof said clappers apart againstthe. action'. of saidiresilient. means; and means. fork connectingxonee of said mounting bands to the extending means whereby said mounting band may move relative to said extending means a distance sufficient to displace said extending means from between said clappers whereafter said tubular member moves with said mounting band whereby the other of said exu tending means will be displaced from between about said fulcrums and holding said clappers apart whereby said cylindrical passage is formed between each pair of clappers and fluid may flow from one line into the other; said last named means moving out of engagement with said clappers when said interconnecting means is disconnected from said lines.

10. A valve mechanism for sealing the ends of a pair of uid lines when the same are disconnected comprising a tubular member adapted to be mounted to the end of each line; a pair of scoop-like clappers mounted within each member, said clappers being mounted on their edge faces for rocking movement relative to each other about fulcrums formed adjacent the larger ends of said clappers; resilient means encircling said clappers and normally holding the edge faces thereof in facewise engagement, said resilient means permitting said clappers to be rocked about said fulcrums to forma cylindrical passage therebetween concentric with said tubular member; and means for interconnecting the open ends ofv said lines, saidrmeans including means extending between the clappers of each tubular member and holding said clappers apart whereby said cylindrical passage is formed between each pair of clappers and uid may flow from one line into the other, the disconnection of said interconnecting means moving said extending means from between said clappers whereby said resilient means of each pair of clappers moves the same together to bring the edge faces thereof into engagement and close the tubular member to a flow of fluid.

11. A valve mechanism for sealing the ends of a pair of iiuid lines when the same are disconnected comprising a mounting band adapted to be mounted to the end of each line; a' pair of scoop-like clappers mounted within each band, said clappers being mounted on their edge faces for rocking movement relative to each other about fulcrums formed adjacent'the larger ends of said clappers; resilient means encircling said clappers and normally holding the edge faces thereof in facewise engagement, said resilient means permitting said clappers to be rocked about said fulcrums to separate the smaller ends of said 'clappers and form a cylindrical passage therethe other of said clappers.

12. A valve mechanism comprising a pair of scooplike clappers; each clapper open at' the large end thereof and having an edge face formed with a pair of fulcrums adjacent the larger end thereof; resilient means for normally holding said clappers with the edge faces thereof in facewise engagement, said resilient means permitting each clapper to be forced about the fulcrums of the other clapper; a casing; means for mounting said clappers in said casing for limited longitudinal movement; means for connecting said casing into a fluid line, said clappers closing said casing to a flow of fluid when said edge faces are in facewise engagement, said casing being open to the flow when said clappers are forced apart about said fulcrums; and means formed internally of said casing for restricting downstream movement of said clappers and for sealing the annular passage between said clappers and said casing when said clappers are closed and the fluid flow is exerting a force against said clappers.

13. A valve mechanism comprising a pair of scooplike clappers mounted on their edge faces for rocking movement relative to each other about fulcrums formed adjacent the larger ends of said clappers, the edge faces of said clappers intermediate said fulcrums and the smaller ends thereof being uniplanar and adapted to form a seal when in facewise engagement; resilient means acting against said clappers intermediate said fulcrums and the smaller ends of said clappers and normally holding said edge faces in sealing engagement, said resilient means permitting said clappers to be rocked about said fulcrums to move said edge faces out of engagement to form a passage between said clappers; a tubular member, said clappers being movably mounted Within said tubular member for longitudinal movement therein; an annular shoulder formed within said member, said shoulder having an inner diameter less than the outer diameter of said clappers when mounted ontheir edge faces and restricting movement of said clappers in one direction longitudinally of said member, said shoulder when said clappers are engaging the same closing the annular passage between said clappers and said member; and means for connecting said tubular member into a fluid line.

14. A valve mechanism comprising a pair of scooplike clappers; each clapper open at the large end thereof and having an edge face formed with a pair of fulcrums adjacent the larger end thereof; means encircling said clappers for resiliently holdingV said clappers with the edger clappers and said casing when said clappers are closed and the pressure is exerting a force against said closed clappers; and means formed integral with said casing and against which the ends of said clappers seat when the force exerted by the pressure of the fluid exceeds a predetermined pressure.

PAUL J. BURCHETT. 

